There has been a continuing need for better athletic footwear. Better cushioning is desirable for protecting the feet, knees and other joints from injury, especially injury resulting from repeated impact, as occurs in running. Cushioning materials, such as foams, are known and used, but these restrict the movement of air in the shoe and act as thermal insulators, making the feet feel warm and causing increased perspiration. Materials that permit unrestricted air circulation around the feet are expected to minimize problems of heat and perspiration. Light weight is another desirable attribute in a shoe material.
Three-dimensional fiber networks are known materials. These are generally derived from textile fabrics that have been impregnated with a thermoset polymer or a low melting thermoplastic and then molded into the desired shape, followed by curing in the case of a thermoset. For the most part, these materials are stiff and are used as lightweight structural materials. For example, U.S. Pat. No. 4,631,221 describes laminates utilizing a rigid three-dimensional fiber network sandwiched between two layers of rigid sheet. The three-dimensional fiber network has a regular series of projections and is impregnated with a thermoset resin, which makes it stiff. U.S. Pat. No. 4,890,877 describes an energy absorbing material for use in automobile doors. The energy absorbing material is made from a highly stretchable lightweight fabric that has been coated with a resin and then shaped into an array of projections. This energy absorbing material after shaping does not appear to have retained its net-like appearance.
The three-dimensional fiber networks known up to now are lightweight and breathable, but they do not appear to have the flexibility to be used in environments where the shape of the network changes repeatedly, nor do they have the resiliency to act as energy absorbing materials.